1. Field of the Invention
The present invention relates to a surface treatment process for fabricating a panel of an organic light emitting device (OLED), particularly to a surface treatment process for fabricating an anti-glare pixel-defining layer on a panel of an OLED.
2. Description of Related Art
The latest OLED dominated a focus of developing flat panel display (FPD) technology in recent years. Compared with other FPDs such as LCDs (liquid crystal displays) and FEDs (Field emission displays), OLED display panels have many distinguished advantages such as light weight, high contrast, fast response rate, low power consumption and high brightness. Although many benefits can be found in the OLED display panels, lots of technical problems in manufacturing OLED display panels still need to be overcome.
So far, the fabrication of OLED display panels is achieved by subsequently forming anode in parallel stripes, parallel photoresist ramparts, organic electroluminescent media and cathodes on the substrate of panels. The parallel photoresist ramparts acts as shadow masks as organic electroluminescent media and cathode materials are deposited on the exposed parallel anodes between photoresist ramparts.
Although the OLED made by the conventional process can adopt as a display, the contrast and the quality of display is limited. In most cases, the contrast of the OLED panels is decreased by or interfered with the ambient light. To improve the contrast of the OLED panels, the application of polarizers is proposed. However, although the polarizer can decrease the interference of the environmental light and increase the contrast of display, the polarizer also decrease the brightness of the OLED panel. This side effect is owning to the emitting-light absorption of the polarizers themselves. For a flat panel display with polarizers attached on both planes, only 38% of the injecting light can pass through the flat panel display with polarizers. Therefore, the conventional polarizers cannot provide a solution for increasing the contrast of the OLED panels without absorption issues and reduce the glare interference of the ambient light.
On the other hand, the lifetime of the OLED panels produced by conventional manufacturing process is not long. The stability of the OLED displays and the yields of these manufacturing processes are poor. The short lifetime and the poor stability of the OLED display panels is resulted from direct contact between anodes and cathode materials in areas close to the border of pixels or the area close to the bottom of the sidewalls of photoresist ramparts. Since the border of pixels are only roughly defined or separated by the photoresist ramparts and the anodes on the substrate, the contact between anodes and cathode materials cannot be effectively prevented. Therefore, the OLED display panels need an effective method to prevent the opportunity of electrical shorts between anodes and cathodes.
Recently, insulation layers made by photoresist are suggested to coated on the surface of the substrate to prevent possible electrical shorts. However, since the insulation layer made by photoresist around pixels"" areas keep releasing organic solvent or water vapor in the OLED slowly, the photoresist insulation layers become major sources of vapors to deteriorate the quality of the sensitive organic electroluminescent media on the OLED display panel. Therefore, the photoresist insulation layers also are the major factor causing short lifetime and poor display quality. Moreover, the photoresists contain many photosensitive chemicals which decrease the photochemical stability of the photoresist insulation layers under high emission and decreased the lifetime of the OLED display panels. In this condition, the photoresist insulation layer is not a right answer to solve the problem illustrated above. Therefore, a method for fabricating a pixel-defining layer on the OLED panel to provide high yield in manufacturing process, good stability of pixel-defining layers for preventing electrical shorts and extending the lifetime of pixels or OLED display panels are urgently in demand.
Therefore, it is desirable to provide an improved method to mitigate the aforementioned problems.
The object of the present invention is to provide a method for fabricating an anti-glare pixel-defining layer on an OLED panel to absorb and filter the ambient light from environment to reduce interference, increase the effectiveness of light emission of the OLED panel, and increase the anti-glare function of the OLED panels.
Another object of the present invention is to provide a method for fabricating an anti-glare pixel-defining layer on an OLED panel to clearly define the area of the pixels on said OLED panel and to separate cathodes from anodes for avoiding shorts.
Another object of the present invention is to provide a method for fabricating an anti-glare pixel-defining layer on an OLED panel for the application in the continuous mass-production of big OLED panels.
To achieve the objects, the method for fabricating an anti-glare pixel-defining layer of the present invention includes:
(A) providing a substrate;
(B) forming a plurality of first electrodes on said substrate;
(C) coating a layer of anti-glare compositions comprising at least
(1) non-photosensitive polyimide or polyimide precursor and
(2) light-absorbing pigments or dyes on said substrate or selectively on said first electrodes;
(D) first prebaking said substrate with said layer of said anti-glare compositions;
(E) coating a layer of photoresist compositions on said layer of anti-glare compositions;
(F) second prebaking said substrate with said anti-glare compositions and said photoresist;
(G) forming patterns of said photoresist through exposing said substrate to masked radiation, developing said photoresist on said substrate, etching said layer of said anti-glare compositions and said photoresist at the same time to form patterned layers of said anti-glare polyimide or polyimide precursor compositions and patterned photoresist; wherein said patterns of said photoresist are as same as said patterns of said layers of said anti-glare polyimide or polyimide precursor compositions;
(H) releasing or stripping said photoresist; and
(I) baking said substrate with said patterned anti-glare polyimide or polyimide precursor compositions for crosslinking or curing said patterned anti-glare polyimide or polyimide precursor compositions to form said anti-glare pixel-defining layers;
wherein said patterns of said layer of said anti-glare polyimide or polyimide precursor compositions divide said first electrodes into a plurality of open areas which are not covered by said anti-glare pixel-defining layers.
The method for forming an anti-glare pixel-defining layer on an OLED panel of the present invention can further includes: (J) forming a plurality of photoresist ramparts on said substrate and selectively on said first electrodes or said stripes of said polyimide pixel-defining layer; wherein said photoresist ramparts protrude from said substrate and the top sections of said ramparts are about parallel to the surface of said substrate.
The method for forming an anti-glare pixel-defining layer on an OLED panel of the present invention can further include: (K) depositing organic electroluminescent media to the exposed area between said ramparts on said substrate or said first electrodes; and (L) forming a plurality of second electrodes on said organic electroluminescent media on said substrate or said first electrodes.
The method for forming an anti-glare pixel-defining layer on an OLED panel of the present invention can selectively further comprising forming a plurality of auxiliary electrodes: on or beneath the surface of said substrate before forming a plurality of, said first electrodes on said substrate.
The method for forming an anti-glare pixel-defining layer on an OLED panel of the present invention can selectively further comprising forming parallel photoresist ramparts having T-shape cross-section on said non-photosensitive polyimide pixel-defining layer, and said patterns of said photoresist are parallel""stripes.
The OLED panel of the present invention comprises: a substrate; a plurality of first electrodes in parallel stripes, said first electrodes locating on the surface of said substrate; a plurality of anti-glare polyimide pixel-defining layers, said anti-glare polyimide pixel-defining layers selectively locating on said substrate or on said first electrodes, and said anti-glare polyimide pixel-defining;layers comprising at least (1) non-photosensitive polyimide or polyimide precursor and (2) light-absorbing pigments or dyes; a plurality of photoresist ramparts, said photoresist ramparts selectively locating on said first electrodes or on said pixel-defining layer; a plurality of organic electroluminescent media, said organic electroluminescent media locating in the exposed area between said ramparts on said substrate; and a plurality of second electrodes, said second electrodes locating on said organic electroluminescent media; wherein each said ramparts protruding from said substrate and having an overhanging portion projection in a direction parallel to said substrate; and said photoresist ramparts are formed through coating a compositions of photoresist on said substrate, exposing said substrate to masked radiation and development.